Twin tube damper with remote gas reservoir

ABSTRACT

A damper is provided having a twin tube construction interconnected to a gas reservoir. The connection of each of the inner and outer volumes of the twin tube to the gas reservoir is independently valved, and each of these valves are independently settable to change the differential pressure thereacross at which they open. The damper provides flow passages directly from the inner and outer volumes to enable flow form the compression to rebound sides thereof, as well as through the valved connections to the gas reservoir and at least one valved opening in the damper piston.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims the benefit of and claims priority to theco-pending U.S. patent application Ser. No. 15/788,653 filed on Oct. 19,2017, entitled “TWIN TUBE DAMPER WITH REMOTE GAS RESERVOIR” byChristopher Paul Cox, assigned to the assignee of the presentapplication, and is hereby incorporated by reference in its entirety.

The application with Ser. No. 15/788,653 claims the benefit of andclaims priority to the U.S. patent application Ser. No. 14/685,348 filedon Apr. 13, 2015, now U.S. Issued U.S. Pat. No. 9,796,232, entitled“TWIN TUBE DAMPER WITH REMOTE GAS RESERVOIR” by Christopher Paul Cox,assigned to the assignee of the present application, and is herebyincorporated by reference in its entirety.

The application Ser. No. 14/685,348 claims the benefit of and claimspriority to the U.S. Provisional Patent Application No. 61/978,620 filedon Apr. 11, 2014, entitled “TWIN TUBE DAMPER WITH REMOTE GAS RESERVOIR”by Christopher Paul Cox, assigned to the assignee of the presentapplication, and is hereby incorporated by reference in its entirety.

BACKGROUND OF THE INVENTION Field of the Invention

The present disclosure relates to the field of dampening devices forvehicles, such as bicycles, motorcycles and four or greater wheeledvehicles. In a further aspect, the disclosure relates to fluid dampershaving lower incidence of cavitation and predictable and user variable,separate, compression and rebound characteristics.

Description of Related Art

Vehicle suspension systems typically include a spring component orcomponents and a damping component or components. Typically, mechanicalsprings, such as metal leaf or helical springs, have been used inconjunction with some type of viscous fluid based damping mechanismmounted functionally in parallel. Dampers commonly include a housingforming a generally fixed volume chamber having a piston therein, whichis attached to a suspension component by a rod or shaft attached theretoand extending from the chamber, and which piston moves axially withinthe chamber to dampen the impact of a suspension force event, such as abump or obstruction in terrain over which the vehicle is moving. Thedamper typically operates by restricting the flow of working fluidacross or through the piston as it traverses the chamber to slow themovement of a piston therein, especially during a compression stroke.The fluid flow restriction elements, because they are located on thepiston which is sealed within the housing, are typically not useradjustable, and are also typically preset for “average” use conditionsand thus are not adaptable to varying conditions.

One variant of the above described damper construct employs a gasreservoir which is coupled to the fluid of the damper across a floatingpiston. The gas reservoir provides a pressure reservoir source which isuseful to cause the piston in the damper chamber to return to a steadystate position after a compression event, also known as rebounding.During a compression event, the physical size of the fluid volume on therebound side of the piston may rapidly increase, and if the fluid flowrate into the rebound chamber is not sufficiently fast, the pressurewill drop in the fluid on the rebound side of the chamber to a levelwhere any gas, such as air, entrained in the fluid will aspirate toreform a gas state thereof, causing cavitation in the fluid. This cancause serious disruption in the proper operation of the damper, andunacceptable noise emanating from the damper.

SUMMARY OF THE INVENTION

There is provided herein a fluid damper having a fluid volume bifurcatedinto a compression and a rebound volume by a fluid piston, and asecondary fluid volume. The bifurcated fluid volume is directlycommunicable with the secondary fluid volume, to enable fluidcommunication and flow between the rebound and compression volumes, aswell as communicable between the compression and rebound volumes throughone or more valved openings in the piston. A gas reservoir is provided,and the gas reservoir is directly communicable to the compression fluidvolume, and is in fluid communication with the rebound volume via thesecondary fluid volume. The communication of at least one of thecompression and rebound fluid volumes with the gas reservoir is valvedto selectively enable or disable fluid communication therewith.

The valves, configured to selectively enable and disable communicationbetween the gas reservoir, are set to open based upon a difference inpressure thereacross, which may be adjustable. Where both thecompression and rebound volume communication to the gas reservoir isvalved, the pressure at which the valves open may be independently setwith respect to one another. In one aspect, the pressure at which thevalve will open is set by urging a secondary force against a shimoverlying an opening in the valve, and a different setting of such forceprovide the variation in the opening pressure setting of the valve.Additionally, the direct communication pathway between the compressionand rebound volumes may have a variable size, which changes as thepiston traverses the damper. This may be provided by positioning aplurality of openings through a tube through which the damping pistonmoves, the openings spaced apart from one another in the direction ofpiston travel, the openings communicable ultimately from the bifurcatedfluid volume to the secondary fluid volume, and from the secondary fluidvolume, to the rebound volume of the bifurcated fluid volumes. As thepiston traverses the tube, different ones of openings communicatebetween the rebound and compression sides of the bifurcated fluidvolume.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the presentinvention can be understood in detail, a more particular description ofthe invention, briefly summarized above, may be had by reference toembodiments, some of which are illustrated in the appended drawings. Itis to be noted, however, that the appended drawings illustrate onlytypical embodiments of this invention and are therefore not to beconsidered limiting of its scope, for the invention may admit to otherequally effective embodiments.

FIG. 1 is a schematic perspective view of an embodiment of the fluiddamper hereof, in accordance with an embodiment.

FIG. 2 is a sectional view of the fluid damper of FIG. 1, showing thedetails of the interior thereof, in accordance with an embodiment.

FIG. 3 is a sectional view of the fluid damper of FIG. 2 at section 3-3,in accordance with an embodiment.

FIG. 4 is a sectional view of the fluid damper of FIG. 2 at section 4-4,in accordance with an embodiment.

FIG. 5 is a sectional view of the fluid damper of FIG. 2 at section 5-5,in accordance with an embodiment.

FIG. 6 is a sectional view of the fluid damper of FIG. 2 at section 6-6,in accordance with an embodiment.

FIG. 7 is a perspective view of the piston of the damper of FIG. 2, inaccordance with an embodiment.

FIG. 8 is a top plan view of the piston of FIG. 7, in accordance with anembodiment.

FIG. 9 is a bottom plan view of the piston on FIG. 7, in accordance withan embodiment.

FIG. 10 is a sectional view of the piston of FIG. 7 at section 10-10, inaccordance with an embodiment.

FIG. 11 is a sectional view of the interconnection housing of FIG. 1 atsection 11-11, in accordance with an embodiment.

FIG. 12 is a partial sectional view of the interconnection housing ofFIG. 1 at section 12-12, in accordance with an embodiment.

FIG. 13 is a partial sectional view of the interconnection housing ofFIG. 1 at section 13-13, in accordance with an embodiment.

FIG. 14 is a partial sectional view of the interconnection housing ofFIG. 1 offset from section 12-12, in accordance with an embodiment.

FIG. 15 is a sectional view of the damper of FIG. 1 showing a firstposition of the damping piston therein, in accordance with anembodiment;

FIG. 16 is a sectional view of the damper of FIG. 1 showing a secondposition of the damping piston therein, in accordance with anembodiment.

FIG. 17 is a sectional view of the damper of FIG. 1 showing a thirdposition of the damping piston therein, in accordance with anembodiment.

FIG. 18 is an enlarged partial sectional view of the interconnectionhousing of FIG. 1 showing the details of a valve thereof, in accordancewith an embodiment.

FIG. 19 is a sectional view of a valve of the interconnection housingshowing details of the detent system thereof, in accordance with anembodiment.

DESCRIPTION OF EMBODIMENTS

A dampening device, such as a strut or shock absorber, generallyincludes a tube shaped housing within which a piston, disposed on an endof a piston rod which extends outwardly of the housing, moves inresponse to forces imposed on the housing and the rod, the movementdampened by the presence of a fluid in the housing passing throughvalved openings in the piston, a secondary reservoir fluidly connectedto the tube, and a connecting portion interconnecting the fluid portionf the tube and the secondary reservoir. Fluid is enabled to move betweenthe housing and the secondary reservoir, in response to movement of thepiston inwardly and outwardly of the housing. Fluid on one side of thepiston is able to move through the piston, to the fluid volume on theopposite side of the piston, through one or more check valves within thebody of the piston. The rate of fluid flow between the fluid volumes oneither side of the piston, and between the fluid volumes in thedampening member housing and the secondary reservoir, affects thedampening effect of the dampening device upon the vehicle in which it isused.

Referring now to FIG. 1, a perspective view of the exterior structure ofsuch a damper cylinder 20 and a remote reservoir 30 are fluidlyinterconnected through a valved interconnection housing 40 which alsobounds one end of the internal pressurizable volumes of the dampingcylinder 20 and of the remote reservoir 30. The valved interconnectionhousing also includes an attachment projection 50 through which a busing52 extends, for attaching the attachment projection 50, and thus one endof the dampening cylinder 20, to a suspension or vehicle framecomponent. At the end 22 of the damping cylinder 20 opposite to theconnection thereof to the valved interconnection housing 40, a pistonrod 60 extends. The distal end 62 of the piston rod 60 surrounds abushed opening 64, through which a bushing 66 extends. The distal end 62of the piston rod 60 is thereby interconnected to the other of one of avehicle frame or suspension components via the busing 66.

The damper 10 is also configured to carry a secondary spring element,specifically a mechanical coil spring 70, for clarity of the laterFigures shown only in FIG. 2, which provides additional rigidity andcompression damping and rebounding force in the damper 10. In thisembodiment, the mechanical coil spring 70 is bifurcated into an upperspring 72 and a lower spring 74. The upper spring 72 extends between,and bears against, an upper annular spring plate 76 secured to the outersurface of the body of the damping cylinder 20, and an upper surface 78of an intermediate annular spring plate 80, which extendscircumferentially outwardly around the circumference of a spring sleeve82, which is configured and sized to fit over, but freely move in anaxial direction over, the damping cylinder 20. The second, lower spring74 extends from contact with the underside annular surface 84 of theintermediate annular spring plate 80, and into contact with a lowerannular spring flange 86 extending outwardly from, and circumferentiallyaround, the piston rod 60 adjacent to, but spaced in the dampingcylinder 20 direction from, the distal end 62 thereof.

Referring again to FIG. 1, the valved interconnection housing 40 alsoincludes two extensions or bosses 42, 44 which provide valved flowpassages (not shown in this Figure) which extend from the dampingcylinder 20 side to the remote reservoir 30 side of the valvedinterconnection housing 40, and, extending approximately normal to theextending direction of bosses 42, 44, an internally threaded boss 46,into which the upper end 22 of the damping cylinder 20 is secured andwhich is fluidly connected to the flow passages and a second boss 48,having a threaded projection 49 thereon (FIG. 2), over which the upperend 32 of the remote reservoir 30 body is secured and the interior ofwhich is fluidly connected to the flow passage. Thus, as will be shownin greater detail in regard to FIG. 2 hereof, upon the movement of thepiston rod 60 inwardly of the damping cylinder 20, fluid within thedamping cylinder 20 may flow from the compression volume in the interiorof the damping cylinder 20, through a flow passage in the valvedinterconnection housing 40, and hence into the remote reservoir 30.Also, during a compression stroke, valves 90, 92 enable flow of fluidthrough the valved interconnection housing 40, and communication offluid pressure, at the gas reservoir pressure, to the rebound side ofthe piston. Likewise, upon retraction of the piston rod 60 from the bodyof the damping cylinder 20, fluid may flow from adjacent the gas piston36 in the remote reservoir 30, through a flow passage in the valvedinterconnection housing 40 and then into the compression volume of thedamping cylinder 20, and fluid, and fluid may flow from the rebound sideof the damping cylinder 20 to the remote reservoir 30, i.e., backthrough the valved interconnection housing 40. The selectablerestriction to flow of fluid inwardly and outwardly of the remotereservoir 30 is provided by valves 90, 92, shown schematically on FIG.1, which will be discussed in further detail herein.

Referring now to FIG. 2, details of the interrelationship of the dampingcylinder 20 and the remote reservoir 30 are shown, wherein the dampingcylinder 20, the remote reservoir 30, and the valved interconnectionhousing 40 are shown in cutaway across a portion of the valvedinterconnection housing 40 intermediate of the two valves 90, 92thereon. As discussed previously herein, a mechanical coil spring 70member having upper and lower springs 72, 74 is disposed about theexterior of the damper cylinder 20. The damper 10 has a main volume 100,surrounded by an inner tube 102, and an annular volume 106 (FIGS. 3 and5), formed between the inner tube 102 and an outer tube 104. Theopenings in the internally threaded boss 46 and second boss 48 of theinterconnection housing 40 enable fluid communication by and between theinner tube 102 volume and the annular volume 106 of the damping cylinder20 and the remote reservoir 30, as will be described in detail herein.

Referring now to FIGS. 2 to 6, the construction of the damping cylinder20 is shown. The fluid volume within the inner tube 102 is bifurcated bythe piston 120 into two variable volumes: a compression volume 108between the piston 120 and the opening of the damping cylinder 20 intothe valved interconnection housing 40, and a rebound volume 109 whichextends between the opposite side of the piston 120 to the inner face ofseal housing 151. Additionally, to provide one of the fluid pathways forfluid communication between the compression volume 108 and the reboundvolume 109, a plurality of openings 110 a-d are provided through thewall of the inner tube 102 between the inner volume of the inner tube102 and the annular volume 106, and a plurality of passages 112 (theplurality shown in FIG. 6) are provided at the interconnection locationof inner tube 102 and the seal housing 151. Thus, during movement of thepiston 120 within the inner tube 102, fluid may flow between thecompression volume 108 and the rebound volume 109 portions of the innertube 102 as the actual volume (size) of those volumes change as thepiston 120 moves within the inner tube 102, from openings 110 a-dthrough the annular volume 106 and into the rebound volume 109 throughthe passages 112, and, if the piston 120 is disposed intermediate of theopenings 110 a-d, for example, wherein opening 110 a is on one side ofthe piston 120 and opening 110 d is on another side of the piston 120,flow may occur therethrough between the rebound and the compressionvolumes 109 and 108, respectively. These un-valved openings 110, andpassages 112 thus provide a direct, though restricted by the crosssection and of the openings, flow pathway for fluid between thecompression volume 108 and the rebound volume 109 during piston 120movement within the inner tube 102.

The openings 110 are configured as a plurality of larger openings 110 a,b and smaller openings 110 c, d and are provided in and through the wallof the inner tube 102 to communicate the main volume 100 (thecompression volume 108 and the rebound volume 109) of the damper 10 withthe annular volume 106 of the damper 10. In this embodiment, as shown inFIG. 2, a large upper and a large lower opening, 110 a, 110 b aredisposed through the inner tube 102 along the sides of the inner tube102 to either side of the inner tube 102, i.e., diametrically opposedacross the circumference of the inner tube 102, and two smaller upperand lower openings 110 c and 110 d are located therebetween, i.e.,between each pair of large openings 110 a, b. Additionally, the openings110 a-d on one side of the inner tube 102, e.g., to the right hand sideof the inner tube 102 are offset, in the direction of the stroke of thepiston 120 toward the valved interconnection housing 40, as compared tothe location of the openings 110 a-d to the left hand side of the innertube 102, but the spacing between the adjacent openings 110 a-d toeither side of the inner tube 102 is the same. As a result, the openingsare staggered along the longitudinal axis L of the inner tube 102. Thus,when a piston, such as piston 120 located within inner tube 102traverses within the inner tube 102 in the direction of the valvedinterconnection housing 40, individual ones of the openings 110 a-d willbe encountered and selectively blocked by the piston 120, and as thepiston 120 passes an opening, the number of openings 110 a-d availableto form a communication path from the annular volume 106 from thecompression volume 108 on one side of the piston 120 to the reboundvolume 109 on the other side of the piston 120, and vice-versa, willchange.

Referring to FIGS. 2, and 7 to 10, the piston 120 is received over areduced diameter, at least partially threaded, end portion 63 of thepiston rod 60, and fixedly connected thereto by virtue of the nut 65 orother fastener threadingly secured on the reduced diameter end portion(distal end 62) to secure the piston 120 between the underside of thenut 65 and a circumferential shoulder 67 on the piston rod 60. The shim124 is secured by the underside of the nut 65 against the compressionside face of the piston 120, and the circumferential shoulder 67 and therebound side face of the piston 120. The piston 120 includes about theouter circumference thereof a plurality of ring shaped lip or othertypes of seals 122, to enable sealing of the piston 120 against theinner surface of the inner tube 102 and thus across the piston 120between the compression volume 108 and the rebound volume 109.Additionally, the piston 120 is configured to enable flow therethroughbased upon the pressure difference between the compression volume 108and rebound volume 109. This is enabled, in this embodiment, by the useof “shims” 124, 126, on either side of the piston 120, which areconfigured to selectively overlay one or more piston openings 128, 130extending through the piston 120 to selectively open fluid communicationbetween the rebound and compression volumes 109 and 108, respectively.The stiffness of the shims, and the number and configurations of theshims, determines the differential pressure at which the shim will bendaway from the piston openings 128 or 130 and thus allow fluid flow froma higher pressure volume to a lower pressure volume directly therethrough.

In the embodiment shown, each of shims 124 and 126 are substantiallyidentical in construct, and are a thin, stiff, but flexible material,such as thin shell sheeting, which is cut or stamped into a trilobularshape as shown in FIG. 8 such that a cutout 132 is provided in threelocations equally spaced about the diameter of the shim 124, 126, suchthat the cutout 132 aligns with every other piston opening 128, 130about a circumference of the face of the piston 120 and a valve plateportion 134 located between the cutouts 132 positioned to overlay one ofeach of the openings 128, 130 on one side of the piston 120. As shown inFIG. 7, cutouts 132 in the shim 124 are positioned on the compressionvolume 108 side of the piston 120 to enable unrestricted access of fluidinto the piston openings 128 of the piston 120, but position the valveplate portions 134 to overlay the piston openings 130 (shown inoutline). Likewise, the shim 126 (FIG. 9) includes cutouts which exposepiston openings 130 exposed to the compression volume 108 at the reboundvolume 109 side thereof. As shown in FIGS. 10 and 124′, when thepressure in the rebound volume 109 is sufficiently greater than that ofthe compression chamber, the valve plate portions 134 of the shim 124may bend away from the surface of the piston 120 to enable communicationthrough the piston openings 130, in this case the piston opening 130,which communication would otherwise be prevented by the presence of thevalve plate portion 134. Likewise, a sufficiently higher pressure in thecompression volume 108, as compared to the rebound volume 109, willsimilarly result in the valve plate portion 134 of the shim 126 to bendaway from the surface of the piston 120 to enable fluid communicationbetween the compression and rebound volumes, 108 and 109, respectively,via the piston openings 128.

Referring again to FIG. 2, the remote reservoir 30 is configured toinclude a gas reservoir and to enable fluid to be received therein,adjacent to but sealed from the gas reservoir, from the damping cylinder20, and is configured as a generally circular tube 31 having a firstthreaded end 32 threadingly attached to the threads on the threadedprojection 49 of the second boss 48 of the valved interconnectionportion 40, and an opposed threaded end 34, within which is threadinglyreceived in a fill valve housing 142 having a fill valve 144 extendingtherethrough. A floating piston 36 (e.g., gas piston) is received withinthe circular tube 31, such that a gas volume 136 and a fluid volume 138are defined at the opposed surfaces of the floating piston 36. Thefloating piston 36 includes an o-ring or other type of seal 140 within,and extending from, a groove about its circumference to seal the gapbetween the floating piston 36 and the inner wall of the circular tube31 of the remote reservoir 30, and the floating piston 36 is notconfigured to enable deliberate flow of fluid or gas therepast. The gasvolume is typically filled with nitrogen or another gas, the pressure ofwhich is user settable at the fill valve 144.

During a compression stroke of the piston 120 within the dampingcylinder 20, i.e., a movement of the piston 120 inwardly of the tube inthe direction I of FIG. 2, fluid in the compression volume 108 of thedamping cylinder 20 can flow through the valved interconnection housing40 and into the fluid volume 138 of the remote reservoir 30, resultingin movement of the floating piston 36 in the direction of the fill valve144 to decrease the size of the gas volume 136. Additionally, fluid inthe fluid volume 138 may communicate through the valved interconnectionhousing 40 to the annular volume 106 of the damper 10, and thus with therebound volume 109 of the damper 10. Likewise, during a rebound strokeof the piston 120, wherein the piston 120 moves in the damping cylinder20 in the direction O of FIG. 2, fluid in the fluid volume 138 of thereservoir may move through the valved interconnection housing 40 andinto the compression volume 108 of the damping cylinder 20, and thefluid pressure in the fluid volume 138 may communicate, and fluid mayflow, through the valved interconnection portion 40 to the compressionvolume 108 of the piston 120. This functionality, as will be describedfurther herein, enables maintenance of the same fluid pressure, ornearly the same fluid pressure, on either side of the piston 120, andthus pressure drops in the rebound volume 109 during a high pistonvelocity, and hence rapid increase in the rebound volume 109, can beprevented or significantly ameliorated.

Referring now to FIGS. 2 and 6, the lower piston rod 60 receivingportion of the damping cylinder 20 is sealed by a seal housing 151located adjacent to, and slightly inwardly of, the lower end 152 of theouter tube 104 of the damping cylinder 20, and which is secured withinthe outer tube 104 by a cover 154 which is threadingly secured withinthe lower end 152 of the outer tube 104. The seal housing 151 includesan inner, sealed bore 156 within which a sleeve shaped seal 158 extendsin the axial direction of the piston rod 60. The plurality of passages112 extend as notches or recesses over a span of the outer circumferenceof the seal housing 151 to enable flow between the annular volume 106and the rebound volume 109 as described herein previously.

The innermost surface of the seal housing 151 is received within thelowermost end of the outer tube 104. The passages 112 communicatethrough the annular volume 106, and thus, when the piston 120 is movingin a compression stroke, fluid may flow between the openings 110 on thecompression volume side of the piston and the rebound volume, andvice-versa.

Referring now to FIG. 2, the lower end of the inner tube 102 alsoincludes a bifurcated landing spool 170 configured as a pair of thinwalled upper cylindrical body 172 and thin walled lower cylindrical body174, each having an outwardly projecting flange 178 at the opposed endsof the bifurcated landing spool 170. A spring 180 is secured between theflanges 178, and in a free state, maintains a gap 182 between thecylindrical bodies 172, 174. During a rebound stroke of the dampingcylinder 20, as the piston 120 is moving in the direction of the sealhousing 151 end of the inner tube 102, the underside of the piston 120may land against the flange 178 of the thin walled upper cylindricalbody 172, and then be further damped in the rebound direction by thespring 180.

Referring now to FIG. 11, details of the structure of the valvedinterconnection housing 40 are shown. The valved interconnection housing40 is configured to form two different paths for the flow andcommunication of fluid between the fluid volume 138 of the remotereservoir 30 and the compression and rebound volumes 108, 109,respectively, of the damping cylinder 20. Specifically, the valvedinterconnection housing 40 is configured to include a rebound valve 90and compression valve 92, such that the compression valve 92 providesselectable throttling of the fluid flow from the damping cylinder 20 tothe remote reservoir 30, and the rebound valve 90 provides selectablethrottling of a return flow path to the rebound volume 109 of thedamping cylinder 20 to selectively throttle the flow of fluid from theremote reservoir 30 to the rebound volume 190 through the annular volume106 of the damping cylinder 20. Additionally, during a compressionstroke of a damping stroke, in the intermediate housing, within thevalved interconnection housing 40 at the opening to the fluid volume 138(FIG. 2) between the valves 90, 92 an open area 190 is formed wherefluid from and to the rebound and compression volumes 109, 108,respectively, of the damping cylinder 20 leaving or entering the fluidvolume 138 of the remote reservoir 30 may pass or intermingle and thus,fluid entering the open area 190 may pass during a compression strokethrough the compression valve 92 and into the fluid volume 138 and openarea 190 to compress the gas volume 136, and, if sufficient fluidpressure is present at the open area 190 as a result of the fluidflowing thereinto during a compression stroke, the fluid may flowthrough the rebound valve 90 and into the annular volume 106 of thedamping cylinder 20 and thus to the rebound volume 109. Likewise, thereverse may occur, wherein during a rebound stroke, fluid moves throughthe annular volume 106 and through the rebound valve 90 to the fluidvolume 138 of the remote reservoir 30, and, if the pressure in the fluidvolume 138 is sufficiently high, the fluid may pass through thecompression valve 90 and into the compression volume 108. As a result,the pressure in the lower pressure portion of the damping cylinder 20,as among the rebound and the compression volumes, 109 and 108,respectively, will be maintained at or nearly at the gas pressure in thegas volume 136, and thus cavitation in the fluid caused by the fluidpressure therein being insufficient to maintain entrained gas in liquidform will not occur.

The valved interconnection housing 40, shown in the section in FIG. 11,is configured to enable separate flows of fluid from the rebound andcompression volumes 109 and 108, respectively, of the damping cylinder20 to the face (damping cylinder side of the fluid flow path) of therebound valve 90 and the compression valve 92, and after flowing throughone of the rebound or compression valves 90 and 92, respectively, intothe open area 190 of the valved interconnection housing 40. To enablethis flow construct, the valved interconnection housing 40 includes twovalved conduits 210 and 220, one of each communicating with one of thecompression volume 108 and the rebound volume 109 (through the annularvolume 106) to the open area 190. Each valved opening is configured torestrict fluid flow, between the damping cylinder volumes and the openarea 190 in both directions of flow, and each flow direction to each ofthe compression volume 108 and the rebound volume 109 is separatelythrottled through a check valve structure, in the embodiment shown inFIG. 11, a shim type valve structure (best shown in FIG. 18).

Referring now to FIGS. 11 to 14, to provide a flow pathway from thecompression volume 108 of the damping cylinder 20 to the open area 190,the valved interconnection housing 40 includes an upper inner tuberecess 230 into which the upper end 232 of the inner tube 102 of thedamping cylinder 20 extends and a ring or other seal arrangement sealsthe connection of the inner tube 102 into the recess 230. To one side ofthe recess 230 is provided a compression side flow passage 210 (alsoknown as the valve conduit 210), which extends from and is in open fluidcommunication with the upper end 232 of the inner tube 102 to anenlarged valve bore 214, within which a compression piston valve 240 isslidingly positioned. The valve bore 214 extends past the compressionpiston valve 240 and into a larger bore 216 which is in direct fluidcommunication with the open area 190 of the valved interconnectionhousing 40. As shown in FIGS. 11 and 14, surrounding the upper end 232of the inner tube 102 is an annular manifold 228, which is bounded bythe outer wall of the upper end of the inner tube 102 and acircumferential inner wall 229 of the valved interconnection housing 40,and which is in open communication with the valve conduit 220 (alsoknown as the rebound side valve passage 220), the opening thereintoopposite to the opening of the inner tube into the compression side flowpassage 210 within the valved interconnection housing 40. The valveconduit 220 opens into an enlarged valve bore 224, within which arebound side valve piston 242 is slidingly positioned. The enlargedvalve bore 224 extends past the rebound side valve piston 240 and into alarge bore 226 which is in direct fluid communication with open area 190of the valved interconnection housing 40.

Referring now to FIGS. 11 to 13, the flow path of fluid during acompression stroke, i.e., when the piston 120 is moving inwardly of thedamping cylinder 20, is shown. Where appropriate, reference will also bemade to FIG. 2. Beginning at FIG. 12, the valved interconnection housing40 is shown in cutaway to demonstrate the flow path into and out of thecompression volume 108. The compression flow path C, shown in dashedline in FIG. 12, occurs when the size of the compression volume 108 isreduced by the moving of the piston 120 (FIG. 2) inwardly thereof. Thefluid in the compression volume 108 flows from the compression volume108, through the valve conduit 210 of the valved intermediate housing40, and thence through the enlarged valve bore 214, through thecompression piston valve 240 and thence into the open area 190 and thefluid volume 138 of the remote reservoir 30. As a result, the floatingpiston 36 will move within the remote reservoir 30 to reduce the size ofthe gas volume 136, thus increasing the gas pressure therein. As thefluid from the compression volume enters the open area 190 as a resultof the inward stroke of the piston 120 in the damping cylinder 20 toincrease the pressure in the open area 190, that pressure iscommunicated with the reservoir side of the rebound side valve piston242. Simultaneously, the pressure in the rebound volume 109 (annularvolume 106) of the rebound side valve piston 242 is decreasing, due toan expansion of the volume of the rebound volume 109. This reducedpressure is communicated to the rebound volume side of the rebound sidevalve piston 242 through the annular volume 106 of the damping cylinder20 (FIG. 2), and thus, a lowering pressure condition is present on therebound volume 109 side of the one side of the rebound piston valve 242,and an increasing pressure condition is present on the open area 190side of the rebound piston valve 242. In a rebound stroke, the reverseflow occurs.

Referring to FIG. 14, the flow of the fluid from the fluid volume 138into the valved interconnection housing 40 is shown. In FIG. 14, theflow is shown as a dashed line along arrow C′ to distinguish it from theflow from the compression volume 108, as the fluid flowing may be fluidwhich originated in the compression volume 108, or may be fluid alreadypresent in the remote reservoir 30 and valved interconnection housing 40when the compression stroke began. As shown in FIG. 14, fluid flows fromthe open area 190 of the valved interconnection housing 40 and into thelarge bore 226, into the enlarged valve bore 224 and through the reboundside valve piston 242 and thence through the rebound side passage 220and into the annular manifold 228 which leads to the annular volume 106.This fluid then flows within the annular volume 106 to enable fluid inthe annular volume 106 to flow through the plurality of passages 112(FIG. 6) and thence into the rebound volume 109 (FIG. 2).

During a rebound stroke, where the piston 120 is moving in the dampingcylinder 20 inner tube 102 in the direction away from the valvedinterconnection housing 40, the reverse of the fluid flow during acompression stroke occurs through the valved interconnection housing 40.As the piston 120 moves in the inner tube 102 in the direction away fromthe valved interconnection housing 40, the fluid pressure in thecompression volume 108 of the damper cylinder inner tube 102 falls, andthe pressure in the rebound volume 109 increases. Likewise, as the fluidis substantially incompressible, the fluid in the rebound volume flowsout of the rebound volume 109, through the plurality of passages (FIG.6) and into and through the annular volume 106, into the annularmanifold 228, and thence through the rebound side passage 220 whereinthe fluid pressure rises at the rebound volume 109 side of the reboundside valve piston 242. Simultaneously, because the volume within whichthe fluid in the compression volume 108 is present is increasing as thepiston 120 withdraws, the pressure in the compression volume 108, andthus in the flow passages between the compression volume and thecompression volume side of the compression piston valve 240 falls. (SeeFIG. 11.) When the fluid pressure at the rebound volume side of therebound valve piston sufficiently exceeds the pressure on the open areaside of the rebound valve piston, the shim on the open area side of therebound valve piston will move to allow fluid to flow through therebound valve piston and into the open area 190 and the fluid volume 138of the remote reservoir 30. As a result, the higher pressure of therebound volume 109 communicates to the open end side of the compressionpiston valve 240, and when the difference in the pressure on the opposedsides of the compression piston valve 240 is sufficient, the shim on thecompression side of that valve will move to allow fluid, which is now atthe pressure of the gas volume 136 of the remote reservoir 30 to passinto the compression volume 108. Thus, the compression volume 108 israpidly brought to the gas pressure of the remote reservoir 30, therebyreducing the likelihood of cavitation in the fluid in the compressionvolume 108.

As the piston 120 moves within the inner tube 102 of the dampingcylinder 20, it will pass over one or more of the openings 110 a-dlocated about the circumference of the inner tube 104. Thus, aspreviously described, secondary flow pathways, in total having differentfluid flow capacities as the openings 110 a-d are opened and closed oneither side of the piston 120, are created. As shown in FIG. 15, thepiston 120 has moved inwardly of the damping cylinder 20 such that thesize of the rebound volume 109 has significantly increased, and the sizeof the compression volume 108 has significantly decreased, as comparedto the sizes thereof in FIG. 2, wherein the damper 10 is in a relaxed ornon-compressed state. As is shown in FIG. 15, the piston 120 has movedin the direction of the valved interconnection housing 40 to pass thefirst of the openings 110 a, specifically 110 a, to the left side of thefigure, such that the annular volume 106 of the damping cylinder 20 nowcommunicates between the compression volume 108 and the rebound volume109. As a result of the reduction of the size of the compression volume108, and the resulting flow of the fluid therein through the valvedinterconnection housing 40 and the remote reservoir 30, the gas piston36 in the remote reservoir 30 has moved to reduce the size of the gasvolume 136 of the remote reservoir 30. Likewise, as described previouslyherein, the fluid pressure in the annular volume 106 increases as fluidflows through the rebound side valve piston 242 from the open area 190and into the annular volume 106 area. Initially, as the piston 120 movesfrom the position thereof of FIG. 2 to the position thereof shown inFIG. 15, the fluid is throttled because the cross sectional area throughwhich it may flow to the rebound volume 109 is limited by the size ofthe plurality of passages 112 (FIG. 6). Once the piston 120 passes thelowermost of the opening 110 a, the total area of the openings throughwhich the fluid may flow from the annular volume 106 of the dampingcylinder to the rebound volume 109 is increased by the cross sectionalarea of the opening 110 a. Additionally, the movement of the piston rode60 which moves the piston 120 inwardly of the damping cylinder 20likewise moves the spring flange 86 (see FIG. 16) thereon in thedirection of the damping cylinder 20, and thus compressing lower spring74, and the increased spring force in the compressing lower spring 74pushes upwardly 9 (in the direction of the valved interconnectionhousing 40) on the spring sleeve 82, which causes compression of theupper spring 72.

As the piston 120 moves further inwardly of the damping cylinder 20,from the position thereof in FIG. 15 to the position as shown in FIG.16, additional openings 110 b and d on the left hand side of the innertube 102 in FIG. 16, and additional opening 110 a on the right hand sideof the opening 110 a, now communicate between the rebound volume 109 andthe compression volume 108 through the annular volume 106 and thepassages 112, further increasing the cross sectional area through whichfluid may flow from the annular volume 106 of the damping cylinder 20into the rebound volume 109 and thereby further reducing the dampingforce effect of the damper 10. Likewise, the floating piston 36 moves tofurther compresses the gas in the gas volume 136 of the remote reservoir30, and the lower spring 74 and the upper spring 72 are furthercompressed and the spring sleeve 82 moves further in over the dampingcylinder 20 in the direction of the valved interconnection housing 40.

FIG. 17 shows the piston 120 moved inwardly of the damping cylinder 20at nearly the maximum stroke thereinto, opening all of the openings 110a-d to both sides of the damping cylinder 20 in the FIG. 17 tocommunication between the rebound volume and the annular volume 106. Inthis position, the spring sleeve 82 is moved nearly into contact with alimiting ledge 260 extending circumferentially from the outer surface ofthe damping cylinder outer tube 104, compressing the upper spring 72 andthe lower spring 74 to near their maximum compression, and the floatingpiston 36 has further moved to further reduce the size of the gas volume136 in the remote reservoir 30 and thus to the highest pressure of thegas therein. In this position, the maximum opening volume of theopenings 110 a-d communicates between the annular volume 106 and therebound volume 109.

During a rebound stroke, when the piston 120 is moving outwardly of thedamping cylinder 20 and the rebound volume 109 is shrinking and thecompression volume 108 is expanding, the opposite flows occur. Thus, asthe piston 120 moves form the position of FIG. 17 to the positionthereof in FIG. 2, openings 110 b, then 110 d, 110 c and 110 a aresequentially passed, each passing of the piston 120 increasing the crosssection of area through which the fluid may flow from the annular volume106 to the compression volume 108. Likewise, as described previouslyherein, the fluid in the rebound volume 109 initially passes throughopenings 112 (FIG. 6) and openings 110 a-d into the annular volume, andthen through the valved interconnection housing 40 into the common area190. From the common area 190, the fluid may also flow into thecompression volume 108. Simultaneously, where the pressure in the gasvolume 138 is initially higher than the pressure in the compressionportion, or the fluid pressure in the compression volume 108 is fallingin comparison to the pressure in the gas volume 138, the gas volume 138will expand to force fluid therein to flow directly into the compressionvolume 108.

Referring now to FIG. 18, which is an enlarged view of the compressionvalve 92 and a portion of the valved interconnection housing 40 withinwhich the compression valve 92 is seated, the configuration of therebound valve 90 and compression valve 92 is shown in detail. Therebound valve 90 and the compression valve 92 are substantiallyidentical in construct, and thus the configuration of the compressionvalve 92 will be discussed in detail, the description applicable to boththe rebound valve 90 and the compression valve 92.

The compression valve 92 is secured within an opening 300 in the boss 44of the valved interconnection housing 40, and includes a sealing headportion 302 which is removably secured in the opening 300 of the boss44, and from which an adjustment member 304 extends inwardly of thevalved interconnection housing 40 and is secured, at the inwardlyprojecting end thereof, on or within the compression valve piston 240.The adjustment member 304 includes a seal head portion (enlarged head)306 portion, from which a shaft 308 extends inwardly of the valvedinterconnection housing 40 from the sealing head portion 302 and into oronto the compression valve piston 240 at the center of a circumferencethereof. Surrounding the connection of the shaft 308 and the compressionpiston valve 240 is a first spring guide 310 which is free to moveaxially and rotationally about the shaft 308. A second spring guide 312is positioned, about the circumference of the shaft 308, generallyagainst the inner terminal face 314 of the sealing head piston 302, andcoil spring 316 is disposed about the outer surface of the shaft 308 andbetween the first spring guide 310 and the second spring guide 312.Additionally, about the outer perimeter of the shaft 308 at the adjacentsurface of the compression piston valve 240 are disposed a plurality ofshim members 340 a-d, similar in construct to those of FIG. 5, and eachadjacent shim member 340 a-d having a different outer diameter oroutermost span, as measured from a center thereof, as compared to thenext adjacent shim of shim members 340 a-d. In construct, the shim 340 aof the largest span or diameter is positioned to overlay the valve bore342 of the compression piston valve 240, and the closest shim thereto340 b has a smaller diameter, the next shim 340 c an even smallerdiameter or span, and the outermost shim 340 d of the smallest span.Although four shims 340 a-d are described, a smaller or larger numbermay be employed. The largest shim 340 a is configured to selectivelycover and seal off first passages 342 extending through the compressionpiston valve 240 as will be described herein. On the opposed side of thecompression piston valve 240, a single shim, configured to selectivelycover and thus seal off only second passages (not shown) of thecompression piston valve 240 is provided.

Referring to FIGS. 11 and 18, by having the enlarged head 306threadingly secured within a threaded bore 318 of the seal head portion302, the compression piston valve 240 is positionable within theenlarged valve bore 214 of the housing 40. Threads 320 of the threadedbore 318 engage threads 322 on the enlarged head 306, and thus rotationof the adjustment member 304 in the bore of the seal head portion 302causes the compression piston valve 240 to move away, or toward, theinner terminal face 314 of the seal head portion 302. The total stoke ofthe compression side (or, rebound side) of the compression piston valve240 is limited in the retraction from the enlarged valve bore 214direction by the compressed length of the coil spring 316. Hence, thecompression (and rebound piston valve) piston valve 240 are maintainedto travel only within the depth or length of the enlarged valve bore214. As shown in FIG. 11 the rebound valve piston position has beenadjusted, relative to that of the compression piston valve 240, in themanner described above. Because the first spring guide 310 and thesecond spring guide 312 are located about the shaft 308, and furtherbounded by the shims 340 a-d in one axial direction of the shaft 308 andthe inner terminal face 314 or the seal head portion 302, drawing thecompression piston valve 240 toward the seal head portion 302 by turningthe enlarged head compresses the coil spring 316, and the oppositerotation direction increases the compression piston valve 240 to sealhead portion 302 distance thereby reducing the spring compression. Theminimum distance between the outermost shim 340 d and the inner terminalface 314 at which the spring 316 will begin to become compressed, is theun-compressed height (i.e., free length) of the coil spring 316 plus thethickness of the flanges 311 on the first spring guide and the secondspring guide 312. Thus, by adjusting the rotational position of theenlarged head 306 in the seal head portion 302, the relative position ofthe compression piston valve 240, and thus, the outermost shim 340 d,and the inner terminal face 314 can be less than the minimum distance atwhich the coil spring 316 will begin to be depressed, and thus the forceof the coil spring 316 bearing against the outermost shim 340 d, and thestiffness of the coil spring 316, may be varied between minimumstiffness, when the compression (or rebound piston valve) piston valve240 is fully extended inwardly of the enlarged bore 214 and fully stiffforce, when the spring is fully compressed when the piston is fullyretracted within the enlarged bore 216 in the direction of the seal headportion 302. At the furthest extension of the compression piston valve240 from the inner terminal face 314 of the seal head portion 302, thecoil spring 316 may be in a totally uncompressed state, and, if desiredby a user, the piston position may be adjusted so that the span betweenthe flanges 311 of the opposed spring guides 310, 312 is greater thanthe free height or uncompressed length of the coil spring 316.Alternatively, by rotating the enlarged head 306 in the seal headportion 302, the spring guides may be brought closer together, to a spanless than the minimum distance, thereby preloading the spring againstthe flanges and thus preloading an additional spring force against theoutermost shim 340 d. Continued turning of the enlarged head 302 in theseal head portion 302 will further increase the load of the preloadingof the coil spring 316 on the outermost shim. Ultimately, it iscontemplated that the span between the first spring guide 310 and thesecond spring guide 312 is equal to the free height of the coil spring316, and in that case the maximum force may be preloaded against theoutermost shim 340 d.

In operation, as the piston 120 in the damper inner tube 102 moves in acompression stroke, hydraulic fluid pressure is increased in theenlarged bore 214 against the damper side face of the compression pistonvalve 240 and thus the passages 342 extending therethrough. When thefluid pressure force acting on the damper side of the shim 340 a exceedsthe combined spring force of the shim stack 340 a-d, the coil spring 316force on the shim stack 340 a-d (if any) and the fluid pressure on thereservoir side of the shim stack 340, the shim stack 340 can lever orbend away from the face of the compression piston valve 240 at thepassages 342 similarly to the opening of a shim 124/124′ shown in FIG.10. Thus, it can be appreciated that during a compression stroke, thestiffness of the damper, is a function of the resistance to fluid flowthrough the several pistons (piston 120, and compression piston valve240 and rebound valve piston) the sidewall openings 110 and passages 112associated with the inner tube 102 of the damper 10, and thus thedamping rate can be adjusted by adjusting the rotational position of theenlarged head 306 in the seal head portion 302 to increase or decreasethe resistance of the shim stack 340 to opening the passages 342.Additionally, as the rebound valve 90 has the same construct as thecompression valve 92, the quantity of fluid moving through the firstpassage 342 will not result in a significant pressure rise on thereservoir side of the compression piston valve 240, because fluid may bereadily vented from that volume through the second passage of therebound valve piston where only a single shim, which is not affected byspring loading, is provided to cover the opening from the reservoir backto the annular volume 106 of the damper 10. The stiffness of the singleshim on the second passage is selected to be less than that of the shimstack 340 a-d. Thus, after a slight pressure rise in the rebound volume109 during a compression stroke, the pressure is relieved via flowthrough the passages on the rebound piston valve 242 of the valvedinterconnection housing 40. Thus, during damping, the reservoirpressure, or nearly the reservoir pressure, may be maintained throughoutthe damper 10, reducing or eliminating cavitation which can occur whenthe pressure on the rebound side otherwise drops as a result of a rapidincrease in the volume of the rebound side of the main housing.

During a rebound stroke, the reverse of the fluid pressure situations,and fluid flows, occur, such that the rebound pressure at the reboundside of the rebound piston valve 242 exceeds the cumulative forces onthe reservoir side of the shim stack, to cause fluid from the reboundside of the piston 120 to begin flowing through passages 112 and intothe annular volume 106, into the opening 128 (e.g., annulus), and thenceincrease pressure at the rebound volume 109 side of the rebound sidewhere the rebound piston valve 242 on rebound valve 90 has greaterspring force acting against the shim stack thereof as compared to thatof the compression piston valve 240 of the compression valve 92, becausethe compression of the coil spring 316 on the rebound valve 90 isgreater than that on the compression valve 92. The stiffness of thesingle shim controlling flow through the second opening of the reboundvalve 90 and the compression valve 92 may be set in consideration of thedesired release of the pressure in the rebound or compression stroke inthe reservoir volume.

Referring to FIG. 19, a detent system to releasably fix the rotationalposition of the shaft 306 in the seal head portion 302 may be provided.The shaft 306 extends through a smaller diameter bore 350 of the sealhead portion 302, and includes therein a finger or cam 352 located in aradially extending slot 354 aligned along the axis of the shaft 308, andhaving a detent spring 356 located between the base of the radiallyextending slot 354 and the underside of the cam 352 within a slot tourge the cam outwardly of the radially extending slot 354 beyond theouter circumference of the shaft 308. Within the smaller diameter bore350 of the seal head portion 302 are provided one or more detent springs356 (eight shown in FIG. 19) extending inwardly of the innercircumferential surface of the smaller diameter bore 350. Where morethan one detent spring 356 is provided, they are equallycircumferentially spaced along the inner face of the smaller diameterbore 350 as is shown in FIG. 19.

As shown in FIG. 18, the enlarged head 306 terminates, outwardly of thecompression valve 92, in a tool boss 360. The tool boss 360 isconfigured to receive a tool therein, which can supply torque to causerotation of the shaft 306 within the seal head 304. Thus, it may beconfigured to include a screwdriver slot or a hex head wrench recess, ormay extend outwardly in a hexagonal profile for location for a wrenchthereover. In this aspect, by providing specific detent springs 356 intowhich the cam 352 can engage, the user of the damper can feel theadjustment degree of the coil spring 316 by specific passing of the cam352 through one or more detent springs 356, and place the cam 352 in aspecific detent spring 356 relating to a compression setting of the coilspring 316 and thus stiffness of the damper 10. For example, the toolboss 360 may include an alignment mark thereon and the boss of thevalved interconnection housing 40 may include a number sequencecorresponding to the position of the cam 352 in the detent spring 356,allowing rapid user understanding of the stiffness setting.Alternatively, a dial structure or knob may be connected to the outerterminus of the shaft, and include numerical settings thereon which canalign with a mark on the outer surface of the bosses 42, 44 to indicatethe rotational setting of the shaft 308 in the seal head portion 302.

The rebound valve 90 and the compression valve 92 are configured forrapid attachment or detachment from the valved interconnection housing40, such as by a threaded annular cap 370 extending about the outersurface of the seal head portion 306 and secured in threads in the bore300, or, by use of a snap ring and groove system, or other readilyopenable securement mechanisms. Additionally, the outer circumferentialsurface of the seal head portion 306 includes a seal bore therein, and aseal such as an o-ring is secured therein the seal the seal head306-bore 300 interface. Thus, valves having different coil spring 316stiffness can be readily interchanged for use in the rebound valve 90and the compression valve 92. Likewise, the mechanically adjusted valvesmay be automated by employing small servo motors, connected to theenlarged head 306, to cause rotation thereof within the seal headportion 306. As a result, the coil spring 316 stiffness/force againstthe shims 340 a-d may be remotely adjusted, and on the fly as the uservehicle is in motion.

There has been described herein a twin tube damper 10, having a maindamping volume surrounded by an annular volume in communication with therebound and compression sides of the main volume, and an interconnectedgas reservoir, wherein the outer tube (annular volume) of the twin tube(inner and annular volume) is communicable with both the compression andrebound sides of the damper, and in which the inner and outer tubevolumes of the twin tube are also communicable with the gas reservoirthrough independent valved access passages. In operation, as describedherein, during a compression stroke of the piston 120 of the damper 10,hydraulic fluid may move from the compression to the rebound side of thepiston through the outer tube (annular volume 106) as well as throughthe valved openings in the piston 120, and, fluid pressure increases atthe compression volume side of the compression piston valve 240 whilstsimultaneously reduces at the rebound side of the rebound piston valve240 in the compression housing. In the event of a slow compressionstroke, the flow capacity of the openings 110 a-d in the wall of theinner tube is sufficient to maintain sufficient flow under the increasedpressure on the compression side and decreased pressure on the reboundside of the piston 120 so as to not cause opening of the shim 126 in thepiston 120, or the shim stack 340 a-d on the compression piston valve240. Where the compression stroke has a higher velocity, such that thevolume of fluid needing to be displaced exceeds the flow capacity of theopenings 110 a-d, the shim 126 will open to open piston opening 130 andthus increase the flow volume area between the compression and reboundvolumes, 108 and 109, respectively, and thus reduce the fluid resistanceof the piston 120 moving in the inner tube 102. If a very rapidacceleration or velocity of the piston 120 is encountered in acompression stroke, where the rebound volume 109 of the damper 10 israpidly expanding and the fluid therein would otherwise reach asufficiently low pressure that cavitation would occur, the shim stack340 a-d will open to open the passage through the compression pistonvalve 240 in the valved interconnection housing 40, immediatelyrelieving the low pressure condition on the rebound side of the volumeand preventing cavitation of the fluid therein. Likewise, in a reboundstroke, if too rapid movement of the piston 120 in a rebound strokeoccurs, the shim stack 340 a-d on the gas piston side of the reboundpiston valve 240 in the valved interconnection housing 40 will open,causing immediate pressure relief and restoration on the compressionvolume 108 side of the piston 120.

The rebound and compression piston valves 240 also serve to damping thepiston 120 movement, and, upon the opening of the piston 240 passage bythe shim stack 340 a-d in a compression stroke, provide an additionalreduction in the resistance to the piston 120 movement in thecompression direction in the inner tube 102 of the damper 10, and anadditional reduction in the resistance to the piston 120 movement in therebound direction in the inner tube 102 of the damper 10 in a reboundstroke. The ability of a user to independently select pressure at whichthe shim stack 340 a-d will open, by varying the spring force againstthe back side of the shim stack, allows user customization of the feelof the ride and thereby enhances user enjoyment of the vehicle on whichthe damper is mounted. Furthermore, the user may select one set ofrebound valve 90 and compression valve 92 spring setting for off roaduse, and another for road use, or even change them as conditions of roador off-road use change, to maximize the user's ride experience.Furthermore, a user may change the entire valve structure rapidly, andthus substitute a compression or rebound valve having different springconstants and/or lengths, and thus different loading characteristics,for a different ride experience.

While the foregoing is directed to embodiments of the present invention,other and further embodiments of the invention may be devised withoutdeparting from the basic scope thereof, and the scope thereof isdetermined by the claims that follow.

I claim:
 1. A fluid damper comprising: an inner tube forming an innerfluid volume; an outer tube forming an outer fluid volume; at least oneflow passage extending through said inner tube to enable fluidcommunication between said inner fluid volume and said outer fluidvolume, wherein at least one opening of said flow passage is not formedin a side wall of said inner tube; a remote reservoir in fluidcommunication with said inner fluid volume and said outer fluid volume,said remote reservoir comprising: a fluid portion; a gas portion; and afloating piston separating said fluid portion and said gas portion; avalved interconnection fluidically coupling said remote reservoir withsaid inner fluid volume and said outer fluid volume, said valvedinterconnection comprising: a first flow passage extending between saidinner fluid volume and said fluid portion of said remote reservoir; asecond flow passage extending between said outer fluid volume and saidfluid portion of said remote reservoir; and at least one valveinterposed in at least one of said first flow passage and said secondflow passage, wherein said at least one valve controls fluid flowthrough said at least one of said first flow passage and said secondflow passage; and a damping piston moveable within said inner tube andconnected to a shaft extending outwardly of said inner tube through asealed end thereof, movement of said damping piston enabling fluid toflow between one side of said damping piston and said fluid portion ofsaid remote reservoir via said valved interconnection and at least oneof said inner fluid volume and said outer fluid volume, said dampingpiston sealingly isolates said inner tube into a compression volume anda rebound volume.
 2. The fluid damper of claim 1, wherein said dampingpiston sealingly isolates said inner tube into a compression volume anda rebound volume, wherein said rebound volume is in continuous fluidcommunication with said outer fluid volume of said outer tube.
 3. Thefluid damper of claim 2, wherein said outer fluid volume is an annularvolume extending around said inner fluid volume.
 4. The fluid damper ofclaim 3, wherein reaching a threshold of a difference in fluid pressureacross said at least one valve in said first flow passage and saidsecond flow passage, thereby achieving a threshold difference in fluidpressure, causes an opening of said at least one valve to open to fluidflow therethrough.
 5. The fluid damper of claim 4, wherein a level ofsaid threshold difference in fluid pressure of said at least one valveis adjustable.
 6. The fluid damper of claim 4, wherein a level of saidthreshold difference in fluid pressure of said at least one valve insaid first flow passage is independently adjustable with respect to alevel of said threshold difference in fluid pressure of said at leastone valve in said second flow passage.
 7. The fluid damper of claim 5,wherein a valve of said at least one valve comprises: a through holeextending therethrough, and a bendable shim extending across saidopening, wherein a bending of said bendable shim away from said openingenables opening of said fluid passage to flow therethrough; and a springplate biased by a spring to selectively press against said shim to urgesaid shim in a direction to close said opening of said valve of said atleast one valve.
 8. The fluid damper of claim 7, wherein said inner tubecomprises: a plurality of openings spaced in a direction of travel ofsaid piston therein and extending between said inner fluid volume andsaid outer fluid volume, said plurality of openings being in an annularwall of said inner tube, and said movement of said position of saidpiston therein exposes different ones of said openings to said fluidvolume of said inner tube on either side of said piston.
 9. The fluiddamper of claim 8, wherein at least a first opening and a second openingof said plurality of openings in said inner tube are spaced part, in adirection of said piston travel, by a gap greater than a width in saidpiston.
 10. The fluid damper of claim 9, wherein said piston is disposedintermediate of said first opening and said second opening, such that,during a stroke of said piston in said direction of said first opening,a first portion of fluid flows from a first side of said piston, throughsaid first opening in said annular wall, and a second portion of fluidsimultaneously flows through said second of said openings and into avolume at said second side of said piston.
 11. The fluid damper of claim10, wherein said first opening and said second opening are in fluidcommunication through an annular volume extending around an innervolume.
 12. A fluid damper, comprising: a first fluid volume partiallybounded by a sealed opening through which a piston shaft extendsinwardly and outwardly of said first fluid volume, said piston shafthaving a piston coupled thereto, said piston located within said firstfluid volume, said piston disposed to separate said first fluid volumeinto a compression side and a rebound side; a first fluid pathwaybetween said first fluid volume and an outer fluid volume wherein atleast one opening of said fluid pathway is not formed in a side wall ofan inner tube; a reservoir comprising: a gas portion; and a fluidportion separated from said gas portion; and a valved interconnectionhousing, wherein said valved interconnection housing includes a firstvalved flow passage extending between said compression side of saidfirst fluid volume and said fluid portion of said reservoir.
 13. Thefluid damper of claim 12 wherein said valved interconnection housingfurther comprises a second valved flow passage extending between saidrebound side of said first fluid volume and said fluid portion of saidreservoir.
 14. The fluid damper of claim 13, wherein at least one valveof said first valved flow passage and said second valved flow passageare adjustable to select a pressure at which they open.
 15. The fluiddamper of claim 14, wherein said at least one valve of said first valvedflow passage and said second valved flow passage are independentlyadjustable, with respect to each other, to select said pressure at whichthey open.
 16. A fluid damper, comprising: an inner tube and an outertube, said outer tube at least partially surrounding said inner tube,said inner tube and said outer tube at least partially defining an innerfluid volume and an outer fluid volume; a damping piston moveablydisposed within said fluid damper, said damping piston coupled to apiston shaft, said piston shaft moveable into said inner tube and alsomoveable out of said inner tube via a sealed opening; a first fluidpathway between said inner fluid volume and said outer fluid volumewherein at least one opening of said fluid pathway is not formed in aside wall of said inner tube; a reservoir, said reservoir furthercomprising: a pressurizable gas volume; a fluid volume; and a floatingpiston, said floating piston disposed between said pressurizable gasvolume and said fluid volume; a first valved passage extending betweensaid inner fluid volume and said fluid volume of said gas reservoir; asecond valved passage extending between said outer fluid volume and saidfluid volume of said gas reservoir; and a valve disposed in at least oneof said first valved passage and said second valved passage, operationof said valve at least partially based upon a threshold value of adifference in pressure across said valve.
 17. The fluid damper of claim16, wherein said first valved passage is located in a valvedinterconnection housing.
 18. The fluid damper of claim 16, wherein saidsecond valved passage is located in a valved interconnection housing.19. The fluid damper of claim 16, wherein said first valved passage andsaid second valved passage are located in a valved interconnectionhousing.
 20. The fluid damper of claim 16, wherein said threshold valueis adjustable.